Re: [PATCH][BTRFS-PROGS][V1] btrfs filesystem df

[Goffredo Baroncelli <kreijack@gmail.com>]

On 10/03/2012 07:46 PM, Ilya Dryomov wrote:
> On Wed, Oct 03, 2012 at 06:46:00PM +0200, Goffredo Baroncelli wrote:
>> On 10/03/2012 05:01 PM, Ilya Dryomov wrote:
>>> "Type" for the first column is probably enough.
>>>
>>> Why is the third column called Chunk-size?  If my understanding is
>>> correct, it's just a break down of Disk_allocated from the summary
>>> section.  If so, why not call it Disk_allocated to avoid confusion?
>>
>> Using everywhere Disk_<something>  was my first attempt. But after
>> some thoughts I decided that these are two different kind of
>> information. It is true that Disk_allocated is the sum of
>> Chunk-Sizes... But my feels is that this is a kind of
>> "implementation details". If some other type of allocation unit will
>> be added to BTRFS, then these will be added to Disk_allocated, but
>> not to Chunk list...
>> I prefer to not change the wording until an enough critical mass of
>> people converge to a unique solution .
>
> It is the chunks that is the implementation detail that we want to hide.
> Average Btrfs user wouldn't want to know anything about chunks, the only
> thing he'd be interested in is Disk_allocated and similar fields.

The "df" standard tool id sufficient for the "average user".
We need only to export these information via the standard syscall 
stat[v]fs. Basically we should try to implement the algorithm of the 
Free_(Estimated) space for the statfs(2) syscall.
Who uses btrfs tools, is an user with knowledge of btrfs higher than the 
average.

> Moreover, I am pretty sure "Chunk-Size" would actually confuse people.
> I stared at your example output for a few seconds trying to comprehend a
> 21GB Chunk-Size on a 72GB partition.  What you call "Chunk-Size" is
> actually a sum of sizes of chunks of that particular type, and a few
> lines above you call the same exact sum (only this time over all types
> of chunks) "Disk_allocated".  So I think it's only logical to rename the
> column in question to "Disk_allocated" to match the summary section.

What about
[...]
Details:
   Chunk_type  Mode      Size_(disk) Size_(logical)     Used
   Data        Single       21.01GB      21.01GB     10.53GB
   System      DUP          80.00MB      40.00MB      4.00KB
[...]

?

Still I am still not entirely satisfied; I am open to other suggestions, 
but until now every people has a different opinion. If we reach an 
agreement between two/three persons (even different from my opinion) I 
will update the patches. Otherwise I suggest to accept these patches "as 
is" because there no is a "general" consensus to a wording...

> Thanks,
>
> 		Ilya
>
Ciao
Goffredo